Hepatic changes in the freeze-tolerant turtle Chrysemys picta marginata in response to freezing and thawing
✍ Scribed by Susan J. Hemmings; Kenneth B. Storey
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 222 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0263-6484
No coin nor oath required. For personal study only.
✦ Synopsis
Select hepatic changes in the freeze!tolerant hatchling turtle\ Chrysemys picta mar`inata\ were studied in response to freezing at -1=4>C and thawing[ Upon freezing\ a small\ selective increase in the liver weight with no increase in body weight was seen suggestive of an hepatic capacitance response[ In all turtles studied\ lobular di}erences in the hepatic content of glycogen were evident] the smaller lobe contained twice as much glycogen as the larger lobe[ The response to freezing and thawing was comparable[ Total hepatic glycogen levels of turtles were reduced ½59 per cent from control levels in the frozen state and recovered to ×79 per cent of control levels in the thawed state[ Compared to the control state\ turtle blood glucose levels were] unchanged after 01 h in the cool state^reduced 17 per cent after 13 h and increased two!fold after 37 h in the frozen state^and increased 3=4!fold in the thawed state[ Thus\ changes in hepatic glycogen metabolism occur without large changes in blood glucose levels[ In turtle liver plasma membranes\ the hepatic a 0 !adrenergic receptor was barely detectable and did not change[ The b 1 !adrenergic receptor was expressed at high levels and\ compared to control levels\ was] unchanged after 01 h in the cool stater educed 19 per cent after 13 h and 39 per cent after 37 h in the frozen state[ On thawing\ this receptor was 49 per cent of control levels[ While catecholamines working through the b 1 !adrenergic receptor may e}ect early hepatic glycogen breakdown in response to freezing\ other factors must be involved to complete the process[ The plasma membrane!bound enzyme g!glutamyltranspeptidase displayed a di}erent pattern of changes indicative of selective modulation] it was increased 1=6!fold over control levels in the cool state^unchanged in the frozen state^and increased 0=7!fold in the thawed state[ The activity of the kidney enzyme was decreased in the cool state and slightly increased in the frozen and thawed states emphasizing the tissue!speci_c nature of the changes in the activity of g! glutamyltranspeptidase in response to freezing and thawing[ The similarities and di}erences of the hepatic changes in response to freezing and thawing in the freeze!tolerant hatchling turtle to those we have previously reported for the freeze!tolerant frog are discussed [ Copyright Þ 1999